As increasing numbers of user functions are incorporated into radio receivers, the complexities of indicating systems have multiplied. Conventional receivers are cluttered with an array of knobs, lights, and meters the interpretation of which is essential to proper receiver use. While knob type indicators are cheap to manufacture they are difficult to read and generally require an external source of illumination for user identification. Conversely, lights and meters are easy to see but are often expensive as extensive associated circuitry must be employed. Finally, a clutter of indicators detracts from the aesthetics of the receiver appearance.
One approach to indicator simplification has been to incorporate a multiplicity of readouts into one indicator. For example, Japan Industries Limited in their receiver model 601M25, coupled a red light emitting diode to the dial scale pointer. Not only does the pointer indicate the frequency to which the receiver is tuned, but it also changes in emitted light intensity dependent on whether the received station is broadcasting in monophony or stereophony.
Light emitting diodes are replacing light bulbs in modern indicating systems. These diodes are known for their long life and, as manufacturers develop LED's of various colors, will prove ideal as indicators. One manufacturer, Monsanto, sells a part (part no. MV5491) having a red and a green LED in the same translucent package. The LED's are wired in parallel and reverse polarity oriented. When current flows through the part in one direction it emits red light, green light being emitted with a reverse current flow. This is one of many parts which is the product of a modern technology and which would be ideally suited in a variety of indicator applications.